Universe: NwS1

       Name: NwS1                                                    [Show more]
       Type: Subroutine
   Category: Universe
    Summary: Flip the sign and double an INWK byte
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * NWSPS calls NwS1


 Flip the sign of the INWK byte at offset X, and increment X by 2. This is
 used by the space station creation routine at NWSPS.


 Arguments:

   X                    The offset of the INWK byte to be flipped


 Returns:

   X                    X is incremented by 2


.NwS1

 LDA INWK,X             ; Load the X-th byte of INWK into A and flip bit 7,
 EOR #%10000000         ; storing the result back in the X-th byte of INWK
 STA INWK,X

 INX                    ; Add 2 to X
 INX

 RTS                    ; Return from the subroutine